1. Field of the Invention
This invention relates to the formation of dye images from a substantially colorless precursor of a preformed image dye. In another aspect, this invention relates to photographic products and processes for providing an imagewise distribution of a reagent such as a photographically active reagent or an image dye-providing moiety and to novel compounds useful therein.
2. Description of the Prior Art
U.S. Pat. No. 3,719,489 describes and claims photographic processes employing initially photographically inert compounds which are capable of undergoing cleavage in the presence of the imagewise distribution of silver ions made available during processing of a silver halide emulsion to liberate a reagent, such as, a photographically active reagent or a dye in an imagewise distribution corresponding to that of said silver ions. In one embodiment disclosed therein, color images are produced by using as the photographically inert compounds, color providing compounds which are substantially non-diffusible in the photographic processing composition but capable of undergoing cleavage in the presence of the imagewise distribution of silver ions and/or soluble silver complex made available in the undeveloped and partially developed areas of a silver halide emulsion as a function of development to liberate a more mobile and diffusible color-providing moiety in an imagewise distribution corresponding to the imagewise distribution of said ions and/or said complex. The subsequent formation of a color image is the result of the differential in diffusibility between the parent compound and liberated color-providing moiety whereby the imagewise distribution of the more diffusible color-providing moiety released in the undeveloped and partially developed areas is free to transfer. Color-providing compounds useful in the above processes form the subject matter of U.S. Pat. No. 4,098,783, a continuation-in-part, of said U.S. Pat. No. 3,719,489.
Compounds disclosed in the aforementioned patents as useful in liberating a reagent in the presence of said silver ions and/or silver complex are sulfur-nitrogen compounds containing the group ##STR1## These 1,3-sulfur-nitrogen compounds may be linear or cyclic in structure, and in a particularly preferred embodiment are cyclic compounds, such as, thiazolidine compounds which comprise a colored dye radical having the chromophoric system of an azo, anthraquinone, phthalocyanine or other dye and a thiazolidin-2'-yl moiety which may be bonded directly to said dye radical or indirectly through an appropriate linking group. For example, the linking group may be --CH.sub.2 CH.sub.2 O-- as in compound (33) at line 10, column 22, of said U.S. Pat. No. 3,719,489, or it may be ##STR2## as in compound (34) in column 35 of said U.S. Pat. No. 4,098,783.
Copending U.S. patent application Ser. No. 500,366 of Howard G. Rogers filed concurrently herewith is concerned with the formation of a color image in a different manner using a different class of 1,3-sulfur-nitrogen compounds. Rather than relying on the differential in diffusibility between the colored parent compound and the liberated dye to form the color image, the ability of 1,3-sulfur-nitrogen compounds to undergo silver ion assisted cleavage is utilized to provide an imagewise distribution of a colored image dye from a substantially colorless precursor of a preformed image dye by employing a moiety comprising a 1,3-sulfur-nitrogen group to maintain said precursor in its substantially colorless form until said 1,3-sulfur-nitrogen group undergoes cleavage imagewise to correspond to the imagewise distribution of silver ion and/or soluble silver complex formed as a function of development of an imagewise exposed photosensitive element.
Copending U.S. patent application Ser. No. 500,415 of James W. Foley also filed concurrently herewith is concerned with yet another class of 1,3-sulfur-nitrogen compounds which may be employed to form a color image from a substantially colorless precursor of a preformed image dye. As disclosed therein, the imagewise cleavage of the 1,3-sulfur-nitrogen group is used to activate the intramolecular cleavage of an amide group for providing a corresponding imagewise distribution of a photographically useful reagent which may be colored, for example, an image dye, or colorless.
The present invention is concerned with another class of compounds which may be used in forming dye images from a substantially colorless precursor of a preformed image dye and with their use in photographic products and processes.